Bohr Effect

• At low ppO_2 in respiring tissues, Hb has lower O_2 affinity so it readily dissociates; increased by ppCO_2 (Bohr effect), Hb dissociation curve shifts to the right as CO_2 produced by aerobic respiration, diffuses out into erythrocytes; reaction occurs:
• Once O_2 has been released, the Hb ‘mops up’ the excess H^+ ions (readily combine to form haemoglobinic acid -HHb) and so acts as a buffer and prevents a drop in plasma pH (acidity of blood does not increase)
• The HCO_3^- ions diffuse out of erythrocyte into the plasma in exchange for chloride ions (Cl^- ions), ‘chloride shift’, ensures no charges in the erythrocyte change
• ~85% of CO2 is transported as HCO_3^- in blood plasma, ~5% of CO2 is transported dissolved in blood plasma and the remaining ~10% is transported bound to haemoglobin (carbaminohaemoglobin)